It is well known in the art to provide hammer drills with the capability to switch between a conventional drilling mode, with rotation only, and a hammer drilling mode employing conventional drill rotation along with a hammer action. The hammer drill is capable of switching between the two modes, and thus eliminates the need for a separate conventional drill.
U.S. Pat. No. 4,232,749 to Rohrbach discloses a hammer drill having a plastic selector slider oriented normal to the axis of drill rotation. The selector slider has ends that protrude from the drill housing on opposite sides, and it has a circular cut-out for a ball located midway between the ends. When the selector slider is pushed to one side, the ball abuts against the back end of a spindle, which limits the rearward axial travel of the spindle. This limit prohibits the spindle from moving back far enough for a ratchet, attached to the spindle, to engage a second ratchet and cause percussion motion. The hammer drill, therefore, operates only in a pure rotational drill mode. When the sliding rod is pushed in the other direction, the ball does not interfere with the spindle axial travel and thereby allows the engagement of the ratchets, with a resulting percussive drilling motion.
While this configuration will switch between the two modes, it has multiple pieces, which is more complicated than necessary and can add to assembly cost when a simple one piece switch design will do as well. It may also be easier for the operator to accidentally bump the switch and change modes when employing the side-to-side motion for switching than if the switch employed a different type of motion in which the operator must grip the switch to change modes. Further, the selector slider requires projections extending from it to limit its side-to-side travel and also latching elements that correspond to latching detents that must be added to the hammer drill housing in order to hold the selector slider in place, to try and avoid an inadvertent change between the two modes of operation.
Other switch configurations allow for a rotation of a handle to switch between the two modes, but use complicated configurations to achieve this result, which adds to the expense of fabrication and assembly of the hammer drill.
For the operator of the hammer drill, a simple and quick way to switch between the two modes, while not adding much weight or size to the overall unit, is desirable. The operator will also appreciate the drill remaining reliable and long lasting, with an adjustment switch for switching between the two modes that will last. Further, the purchaser of the hammer drill will want the switching capability to be an inexpensive mechanism, adding to the capabilities of the hammer drill while not being easy for the operator to inadvertently switch between the two modes of operation. To make the hammer drill inexpensive, the switching mechanism must be easy to fabricate and assemble into the overall hammer drill assembly.
Consequently, the need arises for a new switchable hammer drill that is simple to use as well as reliable, relatively lightweight and inexpensive and also will stay in the mode the operator of the drill chooses so that it will not change modes due to inadvertent contact of the adjustment switch by an operator of the drill.